TS-870S S-Meter pin with repeated RX/TX switching


Kenwood service buletin 10/11/1996

Symptom:
The transceiver must be in the SSB mode, processor turned on, and AGC set to Slow. Repeated switching between transmit and receive may cause the S-mater to pin full scale. At that time, the receiver will mute for a few seconds.

Cause:
Insufficient processing of the AGC circuit.

Solution:
Replace the three EPROMs on the TX-RX board with the new ones listed below.

TX-RX Board X57-4620-00 (2/2)
Ref. Original P/N New P/N 
IC4 27C256PCJJTE 27C256PCJJTF 
IC5 27C256PCJJUE 27C256PCJJUF 
IC6 27C256PCJJVE 27C256PCJJVF 

Procedure:

Remove the bottom cover of the TS-870S


Remove the shield that covers the TX-RX board which is located on the right side of the bottom of the transceiver.


Carefully remove IC4, IC5, & IC6 from their sockets and replace them with the new parts listed above.


reset the transceiver by holding the [A#B] key depressed as power is turned on. 
Caution:

Make sure the pins of the new EPROMs are properly aligned before insertion. New EPROMs tend to have the pins spread aout wider than the socket. The pins can be beat in by pressing each side of the EPROM against a static free work surface.


Avoid touching the EPROM pins. Graps the device from the top and bottom epoxy body ands between thumb and forefinger.


Avoid inserting the EPROMa backwards. 
Only perform this change on units received for service with the exact sympthon listed above.
Use service codes (8): 18(B): X57-4620(P): IC4(C):91 on WSR.
Time required for this alignments is 15 minutes.